System for producing a blended fluid explosive composition



April 16, 1968 L. L. UDY ETAL 3,373,235

SYSTEM FOR PRODUCING A BLENDED FLUID EXPLOSIVE COMPOSITION Filed Jan.23, 1964 l 3 Sheets-Sheet 1 79 INVENTORS LEX L. UDY

3 ROBERT B. CLAY 75 WILLIAM N. BRYAN BY awn 4 ATTORNEY FIGOI A ril 16,1968 Filed Jan. 23, 1964 L. L. UDY T AL SYSTEM FOR PRODUCING A BLENDEDFLUID EXPLOSIVE COMPOSITION 3 Sheets-Sheet 2 f\ El 5 E s 6 g E 5 a a 8.a

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SYSTEM FOR PRODUCING A BLENDED FLUID EXPLOSIVE COMPOSITION Filed Jan.23, 1964 3 Sheets-Sheet 1:;

FIG. 6 E 3 INVENTORS LEX L.UDY (6! A ROBERT B.CLAY

WILLIAM N.BRYAN ATTORNEY United States Patent 3,378,235 SYSTEM FORPRODUCING A BLENDED FLUID EXPLOSIVE COMPOSITION Lex L. Udy, Robert B.Clay, and William N. Bryan, Salt Lake City, Utah, assignors toIntermountain Research & Engineering Co., Inc., a corporation of UtahFiled Jan. 23, 1964, Ser. No. 339,747 11 Claims. (Cl. 259-8) The presentinvention relates to a system for producing a blended fluid explosivecomposition. More specifically, it relates to a method and an apparatusor plant for producing slurry type explosive compositions for use inblasting operations. Still more particularly, it pertains to a system,including method and apparatus, for blending a liquid component with oneor more dry components in the manner to produce a safe, but powerful andetficient explosive material in the form of a liquid slurry which issufficiently fluid that it can be flowed or poured into receptaclesand/or into bore holes. The first named or liquid component preferablyeither includes originally or is later combined with an inorganicoxygen-supplying material prior to incorporation of dry ingredientsuseful as sensitizers, fuels, etc. This oxygen supplying material shouldbe water soluble to a very considerable degree. Ammonium nitrate isusually preferred as the water soluble, although it may consist of ablend of ammonium nitrate and sodium nitrate. In some cases the lattermay be used to the exclusion of the ammonium nitrate for certain specialcompositions. In general, the liquid starting material is usually asolvent, such as water, or a solution of a salt, such as a concentratedaqueous solution of a highly soluble salt which is a potent component ofthe final blasting agent. However, other types of liquids than water oraqueous solutions may sometimes be employed since the apparatus and theprocess are applicable to various materials.

The invention particularly contemplates equipment and methods for makingcharges of flowing liquid-like explosive material which emerge as fiuentthough often viscous liquid slurries. These products may be useddirectly in a blasting hole or location or they may be packaged forsubsequent use. The products are sufiiciently fluid or plastic that theycan be poured or flowed into a receiving vessel or site for efficientfilling of drill holes, etc.

In the prior art it has been shown that fluid compositions of thisgeneral character can be produced by combining a concentrated solutionof an oxygen supplying salt, such as ammonium nitrate, with suitablesensitizers and/or fuels. For example, in US. Patent No. 2,930,685 toCook et al., there is described and claimed an explosive com-position ofthis general type which comprises ammonium nitrate, water andtrinitrotoluene (TNT) as a sensitizer. As set forth in said patent,certain other materials also may be included. While the presentinvention relates rather to equipment and to a process, and is notlimited to the production of particular compositions, it will beunderstood that this invention contemplates the production of explosivematerials such as those described in the Cook et al. patent aboveidentified. It'also relates to a system and process for making othercompositions, including some which have departed from prior concepts,e.g., substitution of other components. Preferably, however, all suchcompositions are sufliciently plastic or fluid that they will flow atleast slowly, so that they may properly be described as fluid orslurried explosives.

One difiiculty that has been encountered in the past in production ofcompositions of this type involves the bringing together and the propermixing of the respective components. For maximum safety, it is desirablethat the separate ingredients be kept apart for as much of the time asis convenient. By combining sensitizers and/or fuels with oxidizers atthe latest practical moment it is possible to substantially reduceexplosion hazards. Obviously, materials of the type described abovecould be mixed in very large batches for high plant efiiciency but forsafety reasons this is not desirable. Obviously, there is alwayspossibility around powerful explosives of a mishap which might detonatea charge. The explosion of such large masses, or even a remote butdistinct chance of such detonation, would be extremely dangerous. Anexplosion if it occurred, would be devastating. Hence, mixing in largebatch mixers comparable to those used for mixing concrete, for example,is considered highly undesirable and usually impractical. One object ofthe present invention is, therefore, to make such batch mixingunnecessary.

Another ditliculty which has arisen in the past in preparation ofexplosive compositions of this type, involves the lack of homogeneity orconsistency from the eginning to the end of a particular batch orcharge. If dry solids are first dispensed, to be joined later by aliquid, it is quite difficult to obtain any degree of homogeneitywithout excessive mixing. Prolonged or energetic mixing of explosiveingredients, of course, is hazardous and is preferably avoided or atleast minimized. One object of the present invention is to make itunnecessary to mix dry ingredients in an energetic or vigorous mannerthat might lead to an explosion. Gentle mixing is made possible by aneffective control over the order and rate at which various componentsare brought together.

A particular aspect of the present invention involves the production offluid explosives in relatively small batches. These batches are smalland relatively safe and each batch can be loaded into a tube or packageof reasonably safe dimensions. For example, if a batch of explosivesweighing 20 to pounds, specifically about 50 pounds, is mixed up anddispensed into a bag and then removed from the equipment, the explosionhazard of such an unconfined charge is not unreasonable. The hazardwould be much greater if the batch were many times as large. Obviously,however, in large scale production, it is desirable to be able toproduce modest sized packages rapidly in succession for economy. Rapidand near-continuous production is necessary to take care of requirementsfor large scale blasting operations. To accomplish such production withreasonable safety is another object of the present invention.

Explosive composition of the general characteristics referred to abovefrequently involve different ingredients having widely varying specificgravities. If sufiicient water or aqueous solution is present to make avery dilute mix, there is likely to be considerable separation andsegregation of the various components, due to their differences inspecific gravity. To avoid such settling or separation, it is desirableto be able to mix a given batch quickly and in such a manner thatsettling does not occur during the mixing. It is also essential that thematerial be so processed, packed and/or thickened that the settling andseparation of components is not likely to occur after the mixing. Toprevent settling and separation during the mixing of the composition,while the slurry is of thin consistency, it is obviously necessary tohave a certain minimum amount of mixing or turbulence imparted to thevarious ingredients. To prevent settling thereafter it is equally anecessary that the finished composition attain such viscosity orstiffnes as to resist substantial separation of its components due togravity. A further object of this invention is to accomplish this.

Combining various components, wet and dry, to make an explosivecomposition of the character to which this invention relates, involvesnecessarily certain hazards. It is frequently desirable to addingredients, usually in dry form, which in themselves are powerfulexplosives, such as trinitrotoluene (TNT), smokeless powder (cellulosenitrate) and the like. In cases where these materials can be finelysubdivided, the problem of separating from a slurry is obviously lessserious than when they are or must be incorporated in larger particlesor pieces. A typical slurry composition, for example, may have anoverall specific gravity of about 1.3. Smokeless powder, on the otherhand, has a specific gravity of about 1.6. Where feasible, the smokelesspowder or the TNT, etc. should be subdivided as finely as is consistentwith economy of preparation and safety of operation.

Another and particular difiiculty that is encountered in mixing liquidmaterials with dry ingredients is that of lack of physical homogeneity.There is frequentiy a tendency for a portion of the charge to be undulyliquid or sloppy whereas other parts of the same charge tend to be toothick or stiff for good fluidity. This obviously contributes to settlingor segregation of suspended particles, which is very objectionable. Thepresent invention contemplates that this tendency can be overcome byfeeding to a'mixing zone the liquid components slightly ahead of the dryingredients and regulating the rate of addition of dry ingredients insuch a manner that a given charge is produced with uniform consistencyfrom top to bottom.

In some cases, a gradual change in composition, from one end of a singlecharge or package to the other may be desired. This invention makes itpossible to produce such a result consistently when desired.

In adding dry ingredients to a system of this type, to which thisinvention pertains, there is also a tendency for the ingredients,particularly when they fall some distance, e.g., due to gravity, toclassify themselves into different particle sizes. It is usually quiteobjectionable, from a standpoint of homogeneity and of quality ingeneral, to have different parts of a given batch or charge filled withcomponents of grain or particle size substantially different from thosein other parts of the same batch or charge. The present invention makesit possible to overcome this tendency by a simple, safe and efiicientmixing procedure. The present process also makes it possible to obtain arelatively dry mix, when desired. Thereby it becomes possible to reducethe proportions of water or of aqueous solution so as to obtain maximumpower in the final product.

For special uses, it is frequently desirable to vary the proportions ofa particular ingredient, or, in some cases, of several ingredients, in apart of a batch. For example, consider a long charge to be placed in abore hole. It may be desirable to have relatively high or hard brisanceproperties at one end of the charge and softer brisance at another.Other properties, such as heat content, etc. may desirably be variedprogressively from one part of a charge or package to another. Thepresent invention makes it possible to accomplish these variations bysimple adjustments of the feed rates of the various components which aresupplied to the mixing zone.

Various other objects will appear and features to achieve them areincorporated in the present invention. These will be more apparent as adetailed description proceeds. The invention, for example, contemplatesincreased safety of the equipment over prior art equipment bypressurizing pneumatically those areas or elements of apparatus where,otherwise, finely divided explosive materials might tend to accumulateand build up dangerous depositions.

The invention further contemplates relatively simple segregation andautomatic control of the proportions of the several ingredients whichare combined into the final explosive slurry composition. Features forthese purposes include separate hoppers or analogous containers for anumber of dry ingredients with variable dispensing means for each suchcontainer. It also includes variable flow rate control means for theliquid component or components, including automatic control means forstarting and stopping the flow of liquid in accura y timed relation tothe starting and stoppage of flow of one or more of the dry or solidingredients. As will be explained in further detail below, this sort ofcontrol contributes very substantially to the satisfactory and rapidproduction of uniform or purposely graded or controlled non-uniformmixes. It will be understood that the term uniform as here used, doesnot necessarily mean that a given charge is completely homogeneous orperfectly uniform in chemical composition at any given cross-section, orfrom one extreme of a charge or package to another. It may indeed becontinuously or gradually variable in one or more of its ingredients,but within the limits imposed by the granular character of theingredients which make up the solids in a slurry, it is obviouslydesirable that the material have a good degree of homogeneity at anygiven point or cross section. For example, in an elongated column orpackage of the composition there is good homogeneity or uniformity inthe macro-particle sense at least, at any given cross section. Thepresent invention has a particular object of accomplishing suchhomogeneity or uniformity.

The invention, then, will be more fully understood by reference to theaccompanying drawings and a detailed description of the particularphysical embodiment therein illustrated. In such drawings:

FIGURE 1 is a vertical sectional view, with certain parts cut away andcertain parts omitted, of a presently preferred apparatus or mechanicalsystem for carrying out the present invention.

FIGURE 2 represents a detailed wiring diagram, shot ing controls forvarious of the elements of mechanical equipment illustrated in FIGURE 1.

FIGURE 3 is another wiring diagram, generally similar to a portion ofFIGURE 2, showing certain modifications in the equipment, particularlyin the electrical control elements.

FIGURE 4 is a horizontal cross sectional view with certain partsomitted, taken substantially on the line 4-4 of FIGURE 1 and lookingdownward as indicated by the line 4-4 of FIGURE 1.

FIGURE 5 is a sectional view, showing a part of the apparatus, takensubstantially on the line 55 or FIGURE 1 and looking upwardly asindicated by the arrows.

FIGURE 6 is a detail perspective view, showing one of the dispensingelements for feeding dry ingredients from one or" the hoppers.

Referring first to FIGURE 1, there is disclosed an apparatus which mayhave a substantial framework, which is not shown, for supporting thesolid and liquid ingredients, etc. Any suitable framing may be used,which will be obvious to those skilled in the art. Thus a foundationstructure with vertical posts or columns, not shown may be provided tosupport a transverse frame member 10 which, in turn, supports a flaredor funnel receptacle element 11 which is adapted to underlie and receiveingredients from a number of hoppers 13, 15, 17 and 19. As seen inFIGURE 4, there are preferably a considerable number of dry ingredientfeeding units, eight of them being shown specifically. However, thenumber may obviously be varied as desired. In this paricular embodimentwith eight hoppers, 13, 15, etc., four are visible in FIGURE 1.

Each of the hoppers 13, 15, etc. has an outlet tube 21 its bottomindicated at 23, 25, 27 and 29 respectively. Each of these tubes joins areceiving trough 31, 33, 35, 37, etc. which is secured to or associatedwith the appropriate tube or downcomer 23, etc., in such a manner thatdry ingredients do not flow unless the trough is moved or vibrated.Hence, under ordinary conditions, the ingredients, such as dry TNT,granular, or aluminum powder, or ammonium nitrate salt or sodium nitratesalt for example, or sulfur or smokeless powder etc., will not flow atall from any of the hoppers unless there is an intentional vibration ormovement of the associated trough.

Associated with each of the feed troughs 31, 33, etc.

is an electrically operated vibrating mechanism. These mechanisms areindicated respectively at 41, 43, 45 and 47 in FIGURE 1. One of them,41, is shown in detail in FIGURE 6. The vibrator device 41 in FIGURE 6is of commercial design and forms, per se, no part of the presentinvention. It consists of an electro-mechanical vibrator box operatingon the solenoid principle, indicated at 48, power being supplied from asource not shown in FIGURES 1 or 6 to leads 49 to cause the supportplate 50 which is attached to the trough 31 to vibrate at a suitablefrequency, for example, 60 cycles per second. The particular frequencyis a matter of choice depending on the type of electric power availableand any suitable vibration speed within the limits of 10 to 100 or morecycles per second is quite satisfactory.

As indicated above, each of the dispensing troughs 31, etc. is attachedto a tube 23 or 25 etc. in such a manner that solids will not flowsimply by gravity but will flow only when the trough is vibrated. Therate of flow depends primarily on the amplitude of the vibrator whichcan be varied at will as explained below. The angle of inclination ofeach trough can .be varied somewhat, depending on the particularingredients involved, but usually runs between about and 20 of slope.

The outlet of each trough 31, 33 etc. is open, as indicated at 53 fortrough 31 at the right of FIGURE 1. This open end overlies the funnel 11which receives the dry ingredients from all the various hoppers 13, 15,17, etc., through the downcomers 23, 25, etc., and the vibrating troughs31, 33, etc. Hence, when any of these troughs is vibrated, ingredientsfrom the appropriate hopper are spilled into the funnel 11.

The walls of the funnel 11 are preferably sloped steeply enough that allingredients will slide freely down them. However, in case a broad funnelis needed, e.g. for multiple hoppers, or in connection with particulartypes of solids such as finely divided powders which do not slidefreely, it may be desirable under some circumstances to attach one ormore vibrators to the wall of the funnel. Such vibrators may be of thesame general type as that shown in FIGURE 6.

As noted above, the funnel 11 is supported in the transverse framemember 10, where it is clamped in suitable fashion for rigid support.The hoppers 13, 15, etc., with their appended outlet and vibrator means,may be supported on the funnel, per se, or may have separate framemember supports, as desired. Below the frame member there is provided atubular mixing vessel 61.

This vessel or receptacle 61 constitutes a mixing zone. Mounted abovethe funnel on suitable support means, not shown in detail, is a powerfulmixing device comprising a motor 63, a shaft 65, and an impeller ormixing blade unit 67. The mixer 67 operates in the lower part of thereceptacle 61. It can be adjusted in height and its propeller-shapedblades are so constructed as to cause a circulatory movement ofingredients from the center of the bottom of the receptacle outwardlyand upwardly as indicated by the arrows. A suitable closure valve 71, ispivotally mounted on a transverse shaft 73 which is appropriatelysupported in suitable journal elements, not shown. This valve can beclosed to hold the ingredients, including liquid,'in the bottom of thereceptacle 61. The valve is shown in its closed position in full linesbut it can be opened as indicated by the dotted lines to discharge thecontents of the receptacle to a receiving tube 75 below.

The receptacle 61 is mounted in frames elements 77, 78, and the tube 75below is mounted on or in a transverse frame element 79. Although notshown in the drawings, the tube 75 which projects below the valve isdesigned to receive a suitable bag or tube for packaging the slurryexplosive in unit packages or charges. Such charges, as noted above, mayvary between about and 100 pounds each.

Means are provided for feeding liquids into the receptacle 61, two suchdevices being shown. In the usual types of slurry compositions a singleliquid, such as a concentrated aqueous solution of ammonium nitrate, is

all that is used. However, for some types of compositions, it may bedesirable to add two, three, or even more liquid components. One or moreof these may be a fuel such as a hydrocarbon oil, or a carbohydratesolution, an alcohol, etc. For this purpose, additional dispensing unitsfor liquid may be employed although not shown in the drawings. At theright of FIG. 1 is shown a main liquid dispenser, indicated generally at80. It comprises a liquid receptacle 81 and a circulating pump 33,preferably of the centrifugal type having an inlet dr'rconnected to thebottom of the tank 81. A recycle line 37 is provided so that when one ormore of the valves in the line 95, such as shown at 89, 91 are closed,the liquid in the receptacle will simply recycle to the tank 81. Thevalve 39 is preferably adapted for a variable setting. Hence itconstitutes a metering device so that the flow rate of liquid, e.g.,water or aqueous solution of an oxidizer salt, may be accuratelycontrolled. Valve 91, on the other hand, is an open-shunt type valvewhich either is fully opened or fully closed. When fully open, the feedrate of liquid through the tube 95 which leads from the receptacle 61 iscontrolled entirely by the adjustment or setting of the metering valve89. The arrangement of pump 83 and Dy-pass line 89 makes it possible tomaintain a rather accurately uniform pressure head on the liquid in line95, regardless of the liquid level in tank 81.

A somewhat simpler dispensing unit for a secondary liquid is shown atthe left, comprising a supply tank or vessel 101, a pump 103, a variableorifice valve and an open-shut valve 167. Both the valves 91 and 107 areadapted to be operated automatically. Where a pneumatic source isavailable they are preferably operated by compressed air, under controlof an electric solenoid of known type. These controls are shown onlydiagrammatically, respectively, at 108 and 109. Operating power issupplied to them by appropriate means, not shown. Here again, the pump103 tends to maintain an even pressure head on the liquid line 1113a,independent of liquid level in tank 101.

Each of the vibrator units 41 has a variable control for its amplitudeof vibration. This is indicated in FIG- URE 6 by the pointer 1 0 whichcan be adjusted to vary the rate of feed of dry materials through theparticular tube and trough with which the vibrator is associated. Hence,by setting the pointers 118 on the various vibrators to appropriatesettings the feed rates of the various dry ingredients in the respectivehoppers 13, 15, 17, etc., may be accurately adjusted.

In addition, the control supplies means by which valve 91 (and 1137 whenthe latter is used) is opened and closed may be operated to open thevalve at any desired instant. In most cases the liquid valve should openbefore the solid ingredients begin to flow. This arrangement makes itpossible to start the liquid feed into the mixer vessel 61 at anydesired instant. The reason for preferring to open the liquid valvefirst is to insure that there will be full and adequate mixing of theliquid and solid components, particularly at the bottom of vessel 61. Ifthe solid ingredients start to llow first, with liquid being addedlater, it has generally been found very difiicult in practice to getfull and adequate mixing of solids and liquids at the bottom of thevessel 61. On the other hand, when liquid flow starts first the solidscan fiow into the small body of liquid which is already in circulationat the bottom of the vessel, due to the operation of the impeller 67.This impeller may be raised or lowered to place it as near the bottom ofthe receptacle (as the bottom is defined by the closed valve 71), as maybe desirable, to insure approariate circulation and mixing of theingreclients.

In a batch type operation, then, the main liquid from vessel 81preferably starts to flow a short time interval before the solidingredients begin to move into the funnel 11. The latter are dispensed,each at the appropriate individual rate, and they fall by gravitythrough the funnel 11 into the receptacle 61. There they meet thedown-flowing primary liquid, e.g. a concentrated aqueous solution ofammonium nitrate from tube 95. The latter liquid may be injected as aspray, if desired, to keep the solids washed down the sides of thevessel. The mixing action of the impeller 67 is usually adequate toinsure a homogeneous charge throughout the mass which accu mulates invessel 61 before the valve 71 opens.

If desired, mixing may be continued after valve '71 is opened orpartially opened. This makes it possible to start feeding a batchthrough tube 75 into a suitable receptacle or container, oralternatively directly to a bore hole where it is to be used, before allthe ingredients have reached vessel 61. Thereafter, when desired, theoperator may vary the composition of the charge as it flows through thevalve 71, by changing proportions or adding or cutting off certaincomponents. Hence by chang ing the feed rate at particular vibrators 41,etc. or varying the intensity or amplitude of the vibration of one ormore of the vibrator units 41, etc., the composition may be varied frombottom to top as it enters a package or a bore hole. 1

The mixing device 67 may be of any suitable type. A commercial mixerknown as the Lightning Mixer, operating at about 300 r.p.m., is quitesatisfactory. However, any suitable mixing device that insuresappropriate circulation at modest velocities and which is not undulyproductive of friction and hence dangerous, may be employed. The devicepreferably has an overload release, not shown, for its driving clutch tocut off power in case the consistency of the mixture around the impellerbecomes too great for relatively low friction operation. This, ofcourse, is a safety precaution.

Ordinarily, in operating the mixing plant, the butterfly valve 71 iskept closed until the batch is fully mixed. It is then opened fully andthe charge, for example, of about pounds weight, flows by gravity intotube and On into the receiver. In a typical operation, a 50 pound bagmay be mixed in about 6 seconds, giving a plant capacity about 500pounds of slurry per minute.

During such a short mixing period, there is generally little or nonoticeable thickening of the composition, even though further slurrythickening in the final state is usually essential. Ordinarily, slurrytype explosive mixes of the character for which this invention isparticularly designed include a thickening agent. This agent is usuallyadded as a dry ingredient in the form of a dry starch or gum. Guar gumis frequently preferred and one of the hoppers 13 or 15, etc.,ordinarily will contain a supply of this material. If guar gum is notused, another thickener will replace it, as a rule. During the normallyshort mixing period, of about 6 seconds, as noted above, there is littleor no noticeable thickening of the slurry. Thickening usually beginsvery soon, however, e.g., within about 15 seconds from the time thethickener is mixed with the liquid. After a period of about 2 minutes atypical batch as dispensed from tube 75 into the eventual receptacle orbag, etc., will be pretty well thickened, reaching something like of itsfinal consistency, in this time period. At such consistency the slurryis quite stable, mechanically. That is to say there is little tendencyfor solid particles to separate from the liquid or from each other andsegregate by gravity. By using small proportions of the thickener, in atypical case about /2 to 1% of guar gum, based on the weight of thetotal mixture, adequate thickening of the slurry in a very short time issecured. This is adequate to prevent the undesirable separation ordifferential gravitation of the particulate components.

The flow of liquid to the mixing zone will ordinarily be cut off at adifferent time from the flow of the solid ingredients. Usually, 11liquid supply from line will be cut off slightly before the flow of theother ingredients is terminated. However, in some cases, it may bedesirable to continue flow of the liquid after the dry ingredients ceaseto flow, in order to flush the walls of the container 61 and thus toprevent accumulation of deposits on such walls.

For feeding a large number of dry ingredients it may be necessary tomake the funnel 11 wider and to increase the angle of inclination of itswalls from the vertical. This may result in a tendency to accumulate drysolids on the funnel walls when the solids, e.g. finely powderedmaterials, do not fall freely down the funnel. in this case, as notedabove, mechanical vibrating means may be attached directly to thesloping wall of the funnel to prevent lodging of the solids.

The plant so far described is entirely suitable for using large particlematerials, such as smokeless powder, TNT and the like, of substantialsize rain. Since the necessary blending is accomplished ordinarilywithin about 5 or 6 seconds and since the slurry begins to set up to agood degree shortly thereafter, n0 considerable difficulty isencountered as a rule, with the settling or segregation of theseingredients. Ordinarily the mixing will not be so rapid or thethickening action so slow or viscosity increase so slow that thickeningaction does not occur with reasonable promptness after the material isdispensed into the receiving package or bore hole.

As noted above, the natural tendency to classification of dryingredients as they fall is largely overcome by the blending action ofthe mixer 67. It is possible in some cases to leave the gate orbutterfly valve 71 open and to mix the dry ingredients into the liquidas they pass by the impeller, allowing the liquid to flow freely toflush solid particles down into the tube 75. By use of a suitableprompt-acting thickener the mixture may be made of adequate uniformityand the required setting up to prevent particulate segregation bygravity can take place after packaging.

Valves 91 and 107 as indicated above, are preferably operated bypneumatic means, controlled electrically. In some cases, however, theymay be operated by a solenoid means equipped with suitable electriccontrols.

It is obvious that, when desired, the feeding of one or more of the dryingredients may be delayed with respect to others. Such timing controlfor feed of various ingredients makes it possible, for example, to addsuch ingredients as smokeless powder (cellulose nitrate) or TNT to onlya part of the charge, for example to the first or the last part. Henceadvantage may be taken of particular characteristics of materials likesmokeless powder or TNT, with low or high brisance, etc. Low brisance atthe top of the charge, for example, will often be more useful than inthe deeper or lower part of the charge.

Referring now to FIGURE 2, there is shown a wiring diagram for a controlpanel. This is only generally indicated at in FIGURE 1. This panelpreferably is pressurized, e.g. by compressed air brought in by a lineAL, to prevent accumulation of explosive powder materials in the panel.Air leakage thus is outward of the panel, not inward. At the right ofFIGURE 2 are indicated diagrammatically the solenoid vibrator meanswhich are incorporated in the respective vibrator mechanisms 41, etc.These are shown respectively at 141, 143, 145, 147, 149, 151 and 155.Each of these solenoids is controlled by a variometer, these beingindicated at 161 to 168, respectively. The control wiring assembly shownin FIGURE 2 is mounted within and on the panel unit 180 as Shown inFIGURE 1. As seen in FIGURE 2, power is supplied to the panel through apair of leads 181 from any suitable conventional power source. A masterswitch 182 is connected to fuses 183, 184. A line 185 from fuse 183 goesto the normal control switch 186 for energizing the circuit. A normallyclosed emergency switch 187 or panic button" is provided, however, whichcan be quickly manipulated to inactivate the whole circuit in case ofdif ficulty. When switch 186 is closed power normally flows from line185 to line 188, thence to inductance 189 and on to line 190. The latterhas two branches, one of which, shown at 191, connects with inductancecoils 192M, 1920 and 1925. Each of these coils has a line 193, 1930 and1935 which connects to a delay timer.' Thus line 193 is connected to anintermediate point of a mixer delay timer 194M, line 1930 connects todelay timer 1940 and line 1938 to delay timer 1948. The other branch 196from line 190 connects to the base terminals 197M, 1970 and 1978 of thethree timers 194M, 1940 and 1948. These timers govern the opening ofvalves 91, 107 and 71, respectively. See FIG. 1. A line 200 from themain control switch 186 connects to a line 201 which in turn isconnected to one of the terminals of each of a series of condensers 202to 213, inclusive.

From the fuse 184 at the power line a line 220 connects to one of theterminals of variometer 161 which controls one of the vibratorsassociated with a device 41, FIG. 6 or 43, etc., FIG. 1. This line alsoconnects to a bus bar or line 221 which connects to the oppositeterminals of each of the variometers 162 to 168, respectively. Switches223 to 230, inclusive, which may be closed individually or in groups asdesired, are provided to energize the variable vibrator elements -141 to155, inclusive. A line 222 which connects the terminals of all theswitches 223 to 230, inclusive, together also connects to a line 241which in turn connects to condensers 209 and 210.

A manually operable switch is shown at 250 to control delay of solidsfeed, this being a double pole-double throw switch. In the on positionshown, it connects a liquid delay timer switch 240 through line 245 andline 246. The line 246 is connected to one of the variometers, 163; thelatter connects with line 221 and completes the circuit.

In the alternative open position, the switch 250' connects line 245 witha line 247. This leads to a 2-pole single throw switch 248. It has thebolts L1 and L2 for operating valves 91 and 187, selectively. Whenswitch 248 in line 247 is in the position shown, it activates a circuit,comprising line 249 and a solenoid 250. The circuit is completed by aline 261 back to fuse 184. As soon as delay switch 240 operates, valve91 will open. The solenoids 252, 250 and 251, respectively, control theslurry valve 71 at the bottom of the receptacle 61, FIGURE 1, the mainliquid valve 91, and the secondary liquid valve 107, respectively.

When switch 248 is moved to the other position, it energizes a line 260.The latter connects to the solenoid 251 and will operate valve 107 assoon as delay switch 240 operates to close the circuit. The delay 240thus is wired and designed to interpose a predetermined time delay oneither the opening of the main liquid valve 91 or the auxiliary liquidvalve 107. A double-pole double-throw switch 270 is provided to leavethe time delay 240 operative, when it is closed, as it is shown in FIG.2. When thrown to the other position, this switch effectively bypassesdelay 240 and activates through line 272 and condensers 206, 207, a,manual switch 280. When the switch 250 is in the on position, as shownin FIGURE 2, current flows from line 245 through delay 240, switch 270,line 275,'and line 244 to condenser 212.

Three manual switches 280, 281 and 282 are provided for controllingvalves 71, 107 and 91 respectively. Switch 280 is for the purpose oftripping the slurry valve 71, which may be operated either byelectrically controlled pneumatic means or by a solenoid. The switches281 and 282 serve to open the secondary liquid valve 107 or to open thetimer liquid valve 91, respectively.

A switch 290 also is provided which may be closed manually to connectthe power line 206 with the main slurry valve control solenoid 252through line 291.

By the means just described and by selective closing of vibratorswitches 223 to 230, or any of them, plus adjustment of the desiredvariometers 161 to 168, inclusive, or such of them as are desired to beoperated, the feed rate of all the ingredients may be accuratelyestablished. The sequence of starting and stopping the feed of anyliquid ingredient may be controlled automatically. All the dryingredients are under a single control, except that variometer 163 andthe associated controls make it possible to delay the feeding of one dryingredient with respect to the others. The functions of certain elementsof the electrical circuit, such as condensers which have not beenspecifically mentioned, will be self-evident to those skilled in theart.

Referring now to FIG. 3, there is shown a modification of that part ofthe electrical circuit which controls the feeding of dry ingredientsfrom the hoppers 13, 15, etc. This modification comprises providing amotor drive for automatically changing the feed rate of certainparticular dry components progressively during a given batch operation.The vibrator elements 141, 143, 145, 147, 149, 151 and 153, also 155 arethe same as in FIG. 2. However, a group of them, i.e., 149, 151, 153 and155 are connected to variometers 365, 366, 367 and 368 which areindividually adjustably attached to a movable operating bar 370. Thelatter is attached to a rotatable arm 371 which is secured to or formspart of a gear element 372. The latter is mounted on an axle suitablysecure to a rigid support, not shown. Gear element 372 meshes with adriving worm 373 on the output shaft of a reversible motor device 374.When the latter is operated, by a suitable control circuit not shown indetail, it progressively changes the setting of variometers 365 to 353which are ganged together by bar 370. The initial feed rate of eachvibrator element 149, 151, etc., is set by adjusting the connection ofeach variometer control arm, 365a, 366a, etc.; to the bar. Once thesehave been adjusted they all move in unison as arm 371 moves up or down,depending on the direction of motor device 374.

The plant or system, and the method or process of this invention, arehighly suitable for the sequential production of a series of batches ofexplosive composition which will be highly uniform in composition,consistency and homogeniety.

To review operation of the system briefly, when it is desired to mix abatch or a series of batches of slurry explosive, appropriate hoppers13, 15, '17, etc. are filled with appropriate solids and tank 81 isfilled with the slurry forming liquid. The latter may be water, in whichcase one of the hoppers will contain a highly soluble oxidizer salt,preferably ammonium nitrate. Ordinarily, the tank 81 will be filled witha concentrated solution of ammonium nitrate, e.g. an /15 (parts byweight) heated ammonium nitrate-water solution. The slurry will normallycomprise 5 to about 25 parts by weight of water, based on 100 parts inthe final composition. Where a concentrated salt solution is used as theslurry-forming liquid, this solution will constitute 50 to of the total.A small proportion of the ammonium nitrate may desirably be replacedwith ano her soluble material such as sodium nitrate, sodiumperchlorate, urea or the like. The solids in proportions of 5 to 95 ofthe total Weight of the final slurry, are to be dispensed from the drymaterial hoppers 13, 15, etc. Such solids may include granulated TNT,nitrocellulose, aluminum powder, sulfur, etc. As a rule, a gel-formingthickener such as guar gum or starch, or gelatin, or two or more ofthese, will be included in the dry ingredients to be dispensed.

The other liquid tank 101 may contain a fuel oil, an aqueous fuel suchas a sugar solution, or a hydrocarbon derivative such as alcohol, glycolor the like.

In operation, when power is turned on, the mixer 67 immediately beginsto rotate. Valve 71 normally will be closed. The valve 91 usually willbe opened first, valve 89 having been set to an adjusted meteringposition. The total quantity of liquid fed from tank 81 is a function ofthe setting of valve 89 and of the time during which valve 91 remainsopen. Pump 83 has adequate capacity to feed a full stream with valves 89and 91 wide open, if desired, and it maintains a substantially constanthead of pressure on the liquid in line 95 under usual operatingconditions regardless of the level of the liquid in tank 81. The same istrue, essentially, of pump 103 and tank 101. The pumps thus are designedto maintain very uniform feed rates for any given setting of valve 89 or105.

After the liquid starts to flow, e.g., a fraction of a second later, oras much as 1 second or more in some cases, the vibrator elements 141,143, etc., are activated. In each case the associated variometer 161,162, etc. will have been preset to give the desired feed rate for itsparticular dry ingredient.

The flow of ingredients continues in a typical case for a period of 3 to5 seconds or so. Thereupon the feeding ceases. Ordinarily, the liquidflow will be stopped first and solids flow stopped very shortlythereafter, e.g. within a second or so. However, liquid flow may becontinued for a short time period after the flow of solids hasterminated to flush down solids that may be adhering to the walls ofvessel 61. Usually this will not be necessary.

After the feeding of all ingredients has terminated, mixing will, in atypical case, be continued for another second or so and then valve 71will be opened automatic-ally. The contents of vessel 51 flow outrapidly by gravity and, where packaging of the slurry is carried out,the contents of vessel 61 discharge flow into the container or packagethrough tube 75. Preferably a plastic closed bottom container, e.g. aplastic bag of appropriate size is applied to the outside of tube 75 toreceive the batch as it is discharged. Automatic packaging mechanism maybe attached to tube '75 if desired.

When auxiliary liquid is to be supplied from tank 101 to the mix, thevalves 91 and 107 may be operated in any desired sequence by theautomatic timer-delay mechanisms of FIG. 2. The impeller-type mixer 67causes good circulation of the ingredients, particularly when liquid isfed before flow of the dry ingredients commences. This impeller shouldbe adjusted to appropriate height above the buttenfly valve 71,depending on volume and consistency of the batch, etc., to insure goodcirculation and mixing. By setting the motor 374 in intermittent ofcontinuous operation, the pro-portions of the dry ingredients, orselected ones of them may be changed by steps or continuously as apackage or borehole is filled.

As previously indicated, the valve 71 may be opened before mixing of thebatch is complete or it may even be permitted to remain open during thewhole mixing operation when the ratio of the flows of liquid and solidsis such that good mixing is accomplished before the ingredients pass outof the mixer. In most cases, however, the valve will be kept closeduntil mixing is pretty well accomplished.

Various modifications may be made in apparatus as Well as in procedure.Instead of using vibrator-trough feeders, chain or auger type feedersmay be used, provided their operation does not create hazards. Where thedry ingredients are explosive per se, the vibrator-type feeders whichnormally do not work the dry materials or cause substantial friction,will usually be preferred.

It will be evident that many other modifications may be made in thesystem, in either its process or apparatus aspects. It is intended bythe claims which follow to cover such variations and modifications aswould occur to those skilled in the art, as far and as broadly as theprior art properly permits.

What is claimed is:

1. A system for sequentially producing a blended slurry-type explosivecomposition in batches of substantially uniform quality and homogeneity,which comprises means for feeding to a mixing zone at an accuratelymetered rate a slurry-suspending liquid, said liquid feeding meansincluding a flow rate control device, a positive on-otf valve and apump, means for feeding granular solids to said zone at a controlledrate, means for blending said liquid and solids in said zone, meansindependent of each other and including said on-oif valve forpredetermining and controlling the sequence and duration of both saidfeedings so as to obtain a homogeneous slurry, and means for controllingdischarge of the blended batch from said zone.

2. A mixing plant for preparing an explosive liquid slurry compositioncomprising, in combination, a tank for slurry forming liquid, a hopperfor granular solid material, means including a pump, variable fiow ratecontrol and a shut-off for feeding said liquid and separate variablerate feeder means for feeding said solid material at predeterminedrates, impeller means for blending said liquid and said solid materialtogether, and automatic selective timed delay means for separatelyinitiating the feed of liquid with respect to the feed of the solidmaterial to avoid non-homogeneous slurry production.

3. Combination according to claim 2 wherein means are included forpumping the liquid under a predetermined pressure head which head issubstantially independent of the level of liquid in the tank.

4. Combination according to claim 2 wherein a vibrator actuated feederis used to feed the solid material at a predetermined and accuratelycontrolled rate.

5. In a system for producing a fluid or slurry explosive comprising aliquid containing suspended particulate material, the combination whichcomprises a liquid supply tank, a mixing zone, an outlet line for liquidfrom said tank to said zone, means for causing the liquid to flowthrough said line at a substantially constant pressure, means foradjusting the flow rate in said line, separate controllably variablerate means for feeding particulate material to said zone for suspensionin said liquid, means for blending said liquid and said particulatematerial together, and means comprising an adjustable and selectivelyoperable flow barrier and a rotary impeller for causing the liquid tocirculate from said barrier and blend effectively with said particulatematerial.

6. In combination, a tank for slurry forming liquid, means connectedwith said tank for dispensing liquid therefrom at a substantiallyconstant pressure which is essentially independent of liquid level insaid tank and flow rate therefrom, variable orifice means for accuratelymetering the How rate, an automatically operable cut-off valve for theliquid fiow from said tank, a mixing vessel adapted to receive meteredliquid, a blending means in said vessel, separate means for accuratelyfeeding each of a plurality of particulate solid materials into saidvessel, and automatic means for differentially timing the initiation ofsaid liquid flow and the start of feeding of the solid materials.

7. Combination according to claim 6 wherein the mixing vessel isequipped with an exit control valve at its bottom, whereby liquid isretained for blending with the solid materials.

8. In combination, a blending vessel having a bottom outlet, a valve forselectively closing said outlet, timed flow meter means for supplying aslurry suspending liquid to said vessel at a controlled rate, positiveon-otf means for cutting off flow of said liquid from said meter, animpeller in said vessel adapted to cause turbulence and recirculation ofliquid above said valve, solid metering means for supplying at least oneparticulate solid material to said vessel at a controlled supply rate,and automatic means operable in various preselected sequences to controlsequentially the opening of said valve, the operation of said flow meterand the operation of said solid metering means.

d. In a system of the character described, the combination whichincludes a mixing vessel having a bottom outlet, a flow control valve insaid outlet, a slurry blender in said vessel, 2. liquid supply tank, aliquid flow line from said supply tank to said vessel, :1 variablemetering means in said line, means associated with said line formaintaingardless of low rate through said metering means, a-

positive automatic cut-off valve in said line, a plurality of hoppersfor solid particulate material, a selectively variable rate feeder fromeach of said hoppers, means for bringing fed particulate material fromsaid hoppers to said vessel, and automatic timed means for selectivelycontrolling the opening of said cut-off valve, the initiation of saidfeeders and the opening of said flow control valve.

10. A system according to claim 9 wherein the variable rate feederscomprise electrically operated vibrator means.

11. A system according to claim 5 which is operable continuously andwhich includes automatic means for variably and selectively controllingboth the sequence and timing of the liquid and particulate material.

References Cited UNITED STATES PATENTS 2,203,980 6/1940 Burt 259952.766391 10/1956 Alspaugh 2598 2,863,651 12/1958 McBride 2591542,887,305 5/1959 Ginneken 2598 3,041,049 6/1962 Tavukawa 259154 ROBERTW. JENKINS, Primary Examiner.

1. A SYSTEM FOR SEQUENTIALLY PRODUCING A BLENDED SLURRY-TYPE EXPLOSIVECOMPOSITION IN BATCHES OF SUBSTANTIALLY UNIFORM QUALITY AND HOMOGENEITY,WHICH COMPRISES MEANS FOR FEEDING TO A MIXING ZONE AT AN ACCURATELYMETERED RATE A SLURRY-SUSPENDING LIQUID, SAID LIQUID FEEDING MEANSINCLUDING A FLOW RATE CONTROL DEVICE, A POSITIVE ON-OFF VALVE AND APUMP, MEANS FOR FEEDING GRANULAR SOLIDS TO SAID ZONE AT A CONTROLLEDRATE, MEANS FOR BLENDING SAID LIQUID AND SOLIDS IN SAID ZONE, MEANSINDEPENDENT OF EACH OTHER AND INCLUDING SAID ON-OFF VALVE FORPREDETERMINING AND CONTRO LING THE SEQUENCE AND DURATION OF BOTH SAIDFEEDINGS SO AS TO OBTAIN A HOMOGENEOUS SLURRY, AND MEANS FOR CONTROLLINGDISCHARGE OF THE BLENDED BATCH FROM SAID ZONE.